An organic light emitting device (OLED) is a planar light source, which has several advantages such as wide viewing angle, compatible with the existing manufacturing processes of planar display devices, fast response time, emitting light without ultraviolet rays, small volume and light weight, and can be driven with direct current. Therefore, OLED has great advantages and development potential in the field of display device or lighting device.
In the manufacturing process of an organic light emitting element, an organic light emitting structure is formed between an anode and a cathode. Then, the anode and the cathode are electrically connected to positive and negative electrodes of an external power supply by conducting wires, respectively. In this way, light rays generated by supplying electrical energy to the organic light emitting structure are extracted from the anode side or the cathode side. However, since the organic light emitting element is a planar light source as mentioned above, several factors affects the voltages for driving two ends of the hole carrier and the electron carrier in the light emitting region of the organic light emitting structure when power of the external power supply is supplied to the organic light emitting element. For example, the length of the conducting wire through which the current passed, or the resistance of the anode or cathode leads to a voltage difference between the two ends of the hole carrier and the electron carrier. This leads to an uneven luminosity of the planar light source, which limits upsizing of the OLEDs.
Taking a conventional OLED lighting device as an example, in order to supply power and prevent uneven luminosity, a thin film electrode contact is disposed on the substrate formed with an OLED lighting element for electrically connecting with an external power source so as to supply power to the organic light emitting structure. Since the substrate of the OLED lighting element is normally rectangular, and the anode/cathode thin film electrode contacts are symmetrically disposed on the substrate, it is possible that they are misplaced in relative to positive/negative electrodes of the power supply device in assembling the OLED lighting element to form a lighting device. Once the anode/cathode electrodes are misplaced, the organic light emitting structure will burn out when electrically connected with the external power supply device and a reverse electric field applied. Therefore, an object of the invention is to increase a luminosity evenness of OLED, and at the same time prevent burn-out of OLED due to the misplacement of the anode/cathode electrodes.